1 abstract 2 human beings are intelligent creatures, but · ... object detection and electronic...

Article: Automation and Steering of Vehicles in Ports - Port Technology 1

Automation and Steering of Vehicles in Ports

1 AbstractThe introduction of containers was an essential move towards the automation in ports. Inorder to be able to manage the ever increasing volume of container movements, it will benecessary to further automate the container handling in the future. This requires new sensorsfor obstacle and object recognition, as well as for track guidance.

This article describes the available technologies, successful projects of port automation andgives an outlook to the near future of process automation.

2 Human beings are intelligent creatures, but...

Humans are extremely intelligent creatures. They recognize complex structures and are ca-pable of reacting to fast changing conditions. Their ability of optical and acoustical observa-tion, e.g. in traffic, are enormous.

However: Unfortunately, a human being tires fast and is unreliable in his reactions. Almostevery traffic accident is caused by human error. Its origin often lays within the physical andmental condition of the individual. Generally, a human being is not made for monotonous,repetitive tasks that are to be carried out fast, exact and reliable. This is a field that is lookingfor automation. Steering cranes and other vehicles in ports are a part of this field.

3 Modern machines and automates are more reliable than workers

During the last 10 years, automation engineering has made considerable progress. This isespecially true for actuated and sensor engineering computer and communication technol-ogy, as well as specialized electronics. Nowadays components and systems capable of car-rying out port specific tasks are more reliable and have a lower cost level. Depending on thelevel of automation, it is possible to do completely without an operator or at least ease theworkload of the operator. The tasks are more or less carried out without errors and underfavorable conditions, this means:

• less or no costs for personnel• utmost reliability in container tracking etc. (EDI)• optimum and careful handling of vehicle and load• less energy consumption, less wear and tear• no accidents, more precise vehicle navigation• faster vehicle navigation, faster transshipment• no stress

Of course, it is not (yet) possible to automate every single task, but with increasing transportvolume, there is an increasing pressure for automation.


4 Cost – Benefit – Analysis:

Figure 1 Cost – Benefit – Analysis

For a transportation job, that is to be carried out only once in a while (e.g. once a day) it isstill sensible to use a driver-guided vehicle. But for a transportation pattern that is repeated,e.g. 100 times per day, an automatically navigated vehicle will pay off. For this calculation, itis, however, necessary to consider the cost for labor, as well as the technical and organiza-tional circumstances for each project.

For continuous mass transport (e.g. 10.000 units per day, bulk cargo, fluids and gases) con-veyor belts or pump systems are usually the appropriate form of transportation.

5 Automation

For industry and ports, a form of partial automation has become established. Actuators andsensors are used for operator support. This is the case with drives, anti-sway-systems, posi-tioning systems, object detection and electronic data interchange (EDI).

It is to be determined for each project, whether it is possible to set up a completely driverlessand operatorless system. Fully automated systems are costly, but for the appropriate appli-cation they can have considerable advantages (see above). The quality of the sensors havebeen improved to such a degree, that their performance sometimes exceeds the humanabilities. However, improvements, especially in the field of optical obstacle detection, are stillpossible and necessary.

The task of automatic positioning and steering of vehicles in general and container cranesespecially, has proven to be well solved. The only problem still is higher velocity, especially,if there is the danger of having people suddenly standing in the way.

There is still the endeavor to try running industrial processes with even less personnel.Automation proceeds while workers are asking for more challenging jobs. Monotonous tasksare to be carried out by machines.

6 Sensors

In order to ensure reliable function of the system, it is essential to use the most suitable sen-sor technology as applicable. It is common knowledge, that optical systems with high capac-ity computers are very reasonable in pricing while highly reliable in their operation, as long asthey are used in extremely clean environments (indoor). They are especially well suited for


complex applications. Unfortunately, they fail if confronted with dirt, snow, rain, etc. In thesecases they need at least special (cleaning) care.

Inductive sensors are usually more rugged, but they are limited in their range.

6.1 One - dimensional Sensors

For quite some time already, wheel encoders, magnetic reference marks and distancemeasuring laser scanners have been used for the position determination of vehicles or ma-chines along rails. It is useful to combine different sensor systems in order to avoid some oftheir disadvantages:

- wheel encoders are sensitive in general and especially with regards to slipping- magnetic marks are not absolutely coded- lasers are easily effected by dust, rain, snow, etc.

Transponders or tags as they have been available for approx. 10 years now, have significantadvantages.

Figure 2 Outline: Principle of Transponder Function


The system basically consist of two components:

1. The Transponder (code carrying) is installed within the runway, near the rail or on anobject. It is not battery powered and protected from damaging environmental influencesby an airsealed casing. Transponders are completely maintenance free and have an al-most unlimited life. Their permanently programmed code is unique. There are variousmodels and configurations of transponders available, all suited for different applications.

2. The Reader supplies the transponder with energy by emitting an electromagnetic field. Inreturn the transponder ‘transmits’ its code, which is then ‘received’ and processed by thereader. This contactless communication between the transponder and its reader is an in-ductive effect using a low frequency magnetic field.

Since the mid 90’s transponders have also been used for positioning in ports, because aspecial antenna reader enables us to register the position of the transponder at a distance ofup to 80 mm with an accuracy of approximately 1 - 5 mm. Larger reading distances (200mm) decrease the positioning accuracy to approximately 5 - 20 mm. The accuracy of eachmeasurement also depends upon the environment. When installing transponders, it is es-sential to maintain a certain distance to large metal constructions and steel reinforcements inthe ground.

Antenna readers of a length of up to 1 m enable the determination of the postion of a rail-bound vehicle at any time, provided, that the transponder spacing is ≤ 1 m. This ensures thatat any time there is at least one transponder within the antenna readers field of view.

This system is extremely accurate and does not show the disadvantages of optical systems.It is even possible to varnish or concrete these systems without effect on their performance.

A transponder positioning system is also suitable for synchronization control of very largecranes, such as goliath cranes (see below). Here it is essential to install transponders onboth sides of the rails. With one antenna on each side of the crane, the simultaneous cross-ing of a transponder on each side is registered. In case the spacing between the transpond-ers is rather large (e.g. 3 m), it is recommended to use wheel encoders for in-between posi-tioning, as described above. The first systems of this kind were commissioned in 1996.


6.2 Two - dimensional Positioning/ Navigation and Vehicle Guidance

Figure 3 Transponder Positioning, crane mountedantenna

For more than 20 years now, inductive guide wires or optical lines (optical contrast) havebeen used for automatic guidance of industrial and port vehicles, e.g. RTGs, etc. This systemis either used for the support of the driver or for driverless so-called Automated Guided Vehi-cles (AGVs). Nowadays, there are approximately 20.000 AGVs in operation in industrial ap-plications. For AGVs, usually additional sensors, e.g. wheel encoders, are used for the sup-port of the guidance system.

Optical systems are often not suitable for port applications (see above). The well knownAGVs used for container transport in the port of Rotterdam are, for example, using trans-ponders as reference marks within the runway. In the last few years, GÖTTING has evenequipped several Transponder Positioning Systems for RTGs:

Koahsiung / TaiwanGöteborg, Stockholm, Malmö / SwedenTermi / ItalySalalah / Oman

Due to the different requirements for the large variety of vehicles, e.g. RTGs, RMGs, BridgeCranes, and VCs or AGVs, there are fundamentally different systems available for automaticpositioning and guidance.

6.2.1 Electromagnetic Lines: Guide Wire etc.

A metal band within or on the runway can be used for AGV guidancewithin the appropriate environment. The sensors located in the frontpart of the vehicle recognize the influence of the metal bands on themagnetic field and thus determine the left or right deviation from theintended track. However, these signals are rather weak and easily

influenced by other metal parts in the vicinity (e.g. metal reinforcements within the runway).


Much stronger signals can be generated by using AC current-carrying guide wires (approx.10 kHz; 100 mA). Therefore this technology has been adapted for industrial applications aswell as for People Movers. This guide wire system is extremely accurate and provides posi-tioning information without interruption.

6.2.2 Electromagnetic Reference Marks: Transponders etc.

Vehicles that are equipped with wheel encoders and steering potenti-ometers and/or inertial sensors, do not need continuous track guidance.In this case it is sufficient to install electromagnetic reference marks atdefined spacings (e.g. 3 m). Magnets or inductive transponders aresuitable reference marks.

When the antenna is crossing one of the reference marks, it is capable of determining thereference mark’s deviation to the left or the right from the center of the antenna. This meas-urement then enables the correction of the vehicles deviation.

Inductive transponders have to be activated by the alternating electromagnetic field of theantenna. Only then are they able to transmit their permanently programmed code via aminiature transmitter to the antenna, which then transfers this signal to the interpreter unit fordecoding and processing. This is a significant advantage to uncoded magnets.Electromagnetic reference marks are recommended for track guiding vehicles (two-dimensional) as well as for positioning rail-bound vehicles (one-dimensional), e.g. conveyormonorails. It is possible to achieve extremely high accuracies.

6.2.3 Optical Systems: Laser etc.

Optical systems are especially well suited for clean environments withfree sight connection between sensor and reference patterns. Some ofthe very first AGVs were guided by lines on the runway. Nowadayscameras and image recognition systems enable the recognition ofrelatively complex patterns and reference marks.

Especially the Laser Scanners have become extremely important. Among these, the barcodescanners are most commonly known. For navigation systems, the Laser Scanner rotatesaround its vertical axis (approx. 8 circles per second). The beam is reflected by referencemarks and returned to the scanner. Then the system determines the angle between the ref-erence marks and the vehicle’s longitudinal axis, which is used for the trigonometric calcula-tion of the position. A navigation laser enables free navigation.

6.2.4 Satellite Navigation: GPS etc.

Since the mid 90s, reasonably priced and reliable satellite navigationsystems are available. The mobile participant (Rover) can determineits position anywhere in the world.

However, unfortunately, there are locally differing errors in the signaltransmission. The use of a reference station (differential GPS) basi-

cally eliminates this error. In this case, the Rover will receive the correction data via RFtransmission from the reference station. This way, accuracies of approx. 3 to 5 m can beachieved.


Even higher accuracies are possible through additional carrier phase evaluation (approx. 2 to10 cm). The integration of external sensors on the vehicle generates stabilized positioningvalues, which has lead to a general acceptance of satellite navigation in suitable environ-ments.

This means, that it is essential for the antenna of the Rover to have a permanent sight con-nection to the satellites. In case there is an interruption of this sight connection, it is essentialto integrate inertial and/or odometric sensors.

The GPS technology is a very elegant solution to the positioning problem, however, it is notentirely unproblematical. It is necessary to point out once more, that positioning may be im-possible in situations where there are signal reflections or satellite shadings. It is recom-mended, to determine for each project, whether GPS is the suitable solution.

GÖTTING manufactures, supplies and integrates all four of the above described systems:

- Guide Wires since 1982- Transponders since 1985- Laser since 1996- GPS since 1997

Figure 4 Comparison of Track Guidance Systems

6.3 Sensor FusionIt is normally not possible to realize a Track Guidance Control System with only one sensor.A combination of different sensors is necessary (sensor fusion).

The sensors are used for position coupling (translation and rotation sensors) and positionbearing (physical lines or bearing marks, ground marks). Figure 5 shows an exemplarymodel:


Figure 5 Example: Sensor fusion (AGV / AGT (Automated Guided Truck))

The vehicle (1) (AGV or AGT) has two driven wheels (2), rotary encoders (4) are located onthe drive motors (3) for position determination (position coupling). In addition, there is asteering potentiometer (7) on the servomotor (6) or front axis (5) for dead reckoning. Alterna-tively / optionally it is possible to use an inertial system (8) with an angular acceleration sen-sor (e. g. gyro (9) ) and a longitudinal (11) and a transversal (10) inertial sensor. This exam-ple uses a mark detection system (transponder reader antenna (12)) for location updating.This mark detection sensor (12) creates a new position reference above each mark (13).Then the position coupling (odometry) is used for guiding the vehicle via the virtual track (14)towards the next mark. Since these marks are coded, it is possible to select new tracks (di-rections) at certain predefined points. This enables turning onto the crossing track (16) viathe branching track (15). In order to be able to also reverse the vehicle, it is necessary tomount an additional antenna on the rear end of the vehicle. Within the sensor fusion control-ler (17), position and heading are determined. Then the Navigation Controller (18) will calcu-late the new steering instruction if necessary. Steering amplifiers (20) or drive amplifiers (19)finally close the loop for the control circuit with the motors. In addition, there is usually a vehi-cle computer, which controls features like load handling and other operative functions.

Figure 6 Example: Track Guided RTG

Figure 6 shows a Van or Straddle Carrier or even an RTG viewed from above. The wheels(2 - 5) are used for steering and driving. In order to be able to guide the vehicle in forwardand reverse direction, it is essential to install two antenna readers (12) on the guided side ofthe vehicle.

6.4 Object Recognition

The industry uses automatically driven vehicles that are able to hitch and unhitch a trailerautomatically. In addition there are systems available which are able to recognize objects,like pallets and containers in their position and size. Optical systems with image processingare especially suited for these applications.


For ports, however, the use of cameras is dependant upon the application and not alwaysrecommended (see above). For suitable applications, these systems have considerable ad-vantages, e. g. for the recognition of container corner-castings.

Object recognizing sensors may be used for fine positioning or even for track guiding thevehicle. In the latter case, the navigation is no longer based on optical marks, but on the ob-jects themselves (e. g. containers).

6.5 Obstacle Recognition

As soon as people are allowed to interfere within an automatically operated complex, it isessential that their recognition is guaranteed. For indoor applications, laser scanners with 5m range have proven reliable for this task. For outdoor applications, however, these opticalsystems create problems especially if they are used in snowy, rainy and dirty environments.But due to extensive efforts of the automobile industry, which is working eagerly on the de-velopment of new radar, laser and ultra-sonic sensors, there are improvements to be ex-pected in the near future.

In order to avoid that obstacles in the way do not unnecessarily stop the flow of transporta-tion, the Navigation Controller is able to decide whether it is possible to drive around a cer-tain obstacle (reactive navigation).

6.6 Data Communication

For terminal automation wireless data communication systems have become irreplaceable.GÖTTING supplies broad band as well as narrow band wireless data communication sys-tems of varying frequency and output power for these applications. Depending on the appli-cation, large band width, large range and interference immunity are required.

Figure 7 Comparison of Wireless Data Communication Systems (near range)


Wireless RF connection is one of the conditions for vehicle automation. This RF connectionenables the transmission of instructions, status and service data.

7 Different Automation Models for Ports

7.1 AGVs in Rotterdam

Well known is the world-wide first extensive application with container carrying AGVs in theport of Rotterdam (NL). Since none of the bidders had been able to supply the full scope ofautomation for the overall system, the supply was subdivided into the fields ‘vehicle’, ‘trackguidance system’, ‘vehicle computer’ (navigation) and ‘traffic control system’. A long period oftime had to pass, before finally HHLA at the port of Hamburg (D) decided to introduce asimilar concept.

Since this kind of vehicle is required to drive underneath the quay cranes for container pick-up and directly next to higher container stacks, GPS is not suitable (shadings, reflections).Optical systems are not suitable due to the weather conditions at Hamburg. Guide wires maybreak due to setting sections of concrete. Therefore it was decided to use transponders forpositioning the AGVs.

7.2 RTGs

The first RTGs equipped with the GÖTTING Transponder Track Guidance Systems werelocated in Göteborg / Sweden and Kaohsiung / Taiwan (in 1995/1996). In the beginning therewere a few problems with humidity within the antennas and EMI from the drives, but theywere defined and overcome by a complete replacement of components. Since then, theseand several other applications have been successfully set into operation.

Year Qty. Location 1995 1 Göteborg / Sweden1995 8 Kaoshiung / Taiwan1996 1 Stockholm / Sweden1996 1 Malmö / Sweden1999 15 Salalah / Oman1999 3 Termi / Italy

Currently are being commissioned:

15 RTGs in Nhava Sheva / India24 RTGs in Tanjong Pelepas / Malaysia 9 RTGs in Hamburg / Germany, etc.


Figure 8 Transponder Positioning System in Göteborg

7.3 Automated Standard Trucks

AGVs, like the ones used in Rotterdam, are usually especially designed vehicles. Thus thecosts per vehicle are correspondingly high. Therefore, it was obvious, that the use of stan-dard vehicles, like e. g. terminal tractors, could reduce these costs. However, until just re-cently, the automation of such vehicles failed due to the expenses for the conversion of theactuators (e. g. gearshift assembly).

The new DaimlerChrysler Trucks, however, now indicate a breakthrough: Apparently the newMercedes-Benz Actros Truck is the world-wide first to be equipped with the newCAN bus vehicle components like steering motor, speed control, transmission configuration,brakes etc. These vehicles require little effort for the conversion to automatic operation. Inaddition, it is at any time possible to switch from automatic operation to manual operation,which enables the use of the automated vehicles also in manual mode as normal public roadvehicles.

Advantageous are the low purchase costs and the similarly low operational and maintenancecosts. They are approximately 40 – 50 % lower than those for the known container AGVs.These trucks are mass produced and therefore extremely well tested. Mercedes-Benz, to-gether with Freightliner (USA), is part of the DaimlerChrysler Group, which is currently theworld’s largest truck manufacturer.

GÖTTING was the first to equip one of these Actros trucks with GPS for track guidance,which was then presented to a large international press audience in July 1999. For this demothe truck was not only able to automatically steer forward at a relatively high speed, but alsoreverse the truck with trailer into its parking position at an accuracy of approximately 4 cm!For port applications the use of transponder positioning systems for track guidance will bemore suitable than GPS (see above). In this case the accuracy of the track guidance systemwill be approx. 2 cm. AGVs and AGTs both have their different advantages.


• AGV: better maneuverability• AGT: low purchase, maintenance and operation costs, good reselling value, automatic or

manual operation possible, higher speed.

The most important fields of application for AGTs are, however, outside the port environ-ments.

Figure 9 Automatic DaimlerChrysler Actros during demo in Papenburg, Germany


7.4 GPS Guided RTG

Genoa will be the first port to have GPS guided RTGs (6 units). For this system, the GPSposition will be supported by rotary encoders. The positioning system is designed for an ac-curacy of +/- 5 cm. Since the system itself is again a sensor system which will output theposition (similar to the transponder positioning systems), for us it is essential to cooperatewith competent partners for assembling the complete automatic track guidance system (forthis project, our partner is General Electric).Since RTGs in container stacks always travel along predefined straight lines, the GPS (or thetransponder positioning system for other projects) output the current deviation of the craneposition from the reference line. This is done automatically for an almost indefinite number ofstacks within one terminal. Following the sensor fusion, which generates a position back-upof the odometric position through the absolute position sensor, the value of the deviation istransferred to the vehicle control, usually a PLC, via customized interfaces. Then the vehiclecontrol assesses the vehicle dynamics and generates the control variable for the steeringactuators.

7.5 Service Vehicles

It is not only possible to automate heavy load vehicles, but the automation of service vehi-cles, e. g. for the inspection of container trains, is also very useful. At relatively low speeds,transponder positioning systems are suitable, however, for higher velocities (e. g. 80 km/h) aguide wire system offers more stability.

Figure 10 Track Guided Service Vehicle at the Eurotunnel (F – GB)


7.6 Multi-Trailer Systems and Bulk Cargo Transporters

It is planned to set the first project, which will include a total of three Mercedes trucks, typeActros) with four trailers each (4 x 40 t), into operation during the second half of 2000. Theterminal tractor will automatically hitch and unhitch the trailers. This AGT will always tow aloaded set of trailers I from point A to point B; there it will autonomously unhitch the set I andhitch an other already waiting set of trailers II in order to tow it from B to A. At this point it willagain exchange trailers and repeat the routine with the already loaded set of trailers III etc.

Figure 11 Terminal tractor during automatic shunting and hitching (multi-trailer system)

In addition, the use of heavy duty Actros trucks is planned for bulk cargo transportation. Thevehicles are loaded by a excavator and then carry their load to a riddle construction. At thispoint the load is dumped backwards and the AGTs return to the loading point.

A combination of different systems is going to be used for track guiding these vehicles:Transponders, GPS and Guide Wire for certain sections. In addition there will be cameras onthe vehicles and along the track, since the control post located approx. two kilometers fromthe track has to be informed of the situation at any time.

Figure 12 Loading a bulk cargo truck


7.7 Future Systems

It is already possible to have trucks driving in convoy while only the first truck in line has adriver. Instead of a multi-trailer system, this enables creating a multi-truck system. Thesevehicles have a contactless connection with each other via a so-called “electronic drawbar“(spacing approx. 4 m). This kind of convoy (called “Load Trains“) requires less personnel,energy and road space than single trucks. These vehicles are therefore well suited for thetransport between ports, plants and other large transshipment places.

Figure 13 Convoy of two trucks with electronic drawbar

For most vehicles (AGV, AGT, RMG, RTG, etc.) the task of track guidance has been solvedsatisfactorily. Even VCs will soon be able to steer and operate automatically. Significant im-provements, however, are still to be expected for object and obstacle recognition sensors.Even future terminals will not be ‘unmanned’. Therefore, safe automatic recognition of peopleis the most important requirement for further success with the automation within and outsideport environments.

8 Summary

The new sensor technologies, wireless communication systems, and computers have en-abled new concepts of automation, and this enables ports to introduce more and more auto-mated processes, because reliability and cost reduction are the key issues.


9 About the Author

Hans-H. GöttingHans-Heinrich Götting graduated from the Fachhochschule Han-nover (Germany) in 1979 with a degree in Diplomengineering (Dipl.-Ing.), he then took his MSEE at Newark, New Jersey (USA). Havingfinished university, he entered GÖTTING KG, Lehrte (Germany) andhas been heading this company as general manager since 1986.

GÖTTING KG is a world-wide leading engineering company for sen-sors for track guiding so-called AGVs.

10 Inquiries

If you have any inquiries regarding the content of this article, please contact:

Götting KGMs. Silke Schael

Celler Str. 531275 LehrteGERMANY

Tel. +49 (0) 51 36 – 80 96 -83Fax +49 (0) 51 36 – 80 96 -80

e-mail [email protected] www.goetting.de

1 abstract 2 human beings are intelligent creatures, but · ... object detection and electronic...

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